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These documentation source files are not the one true version, just a copy for testing purposes. DO NOT EDIT THESE FILES. To use this on Windows you will need a working asciidoc installation and the path to it must be included in your CMAKE_PREFIX_PATH (probably via a local CMake tool chain file). At the time of writing the official asciidoc package does not work on Windows. The latest development master does however work, it can be downloaded as a snapshot ZIP archive from here: https://github.com/asciidoc/asciidoc/archive/master.zip git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5316 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
22 lines
1.1 KiB
Plaintext
22 lines
1.1 KiB
Plaintext
// Status=review
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//Needs work!
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JT9 is designed for making minimally valid QSOs at LF, MF, and HF. It uses
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72-bit structured messages nearly identical (at the user level) to
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those in JT65. Error control coding (ECC) uses a strong convolutional
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code with constraint length K=32, rate r=1/2, and a zero tail, leading
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to an encoded message length of (72+31) × 2 = 206 information-carrying
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bits. Modulation is nine-tone frequency-shift keying, 9-FSK.
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Eight tones are used for data, one for synchronization. Eight data
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tones means that three data bits are conveyed by each transmitted
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information symbol. Sixteen symbol intervals are devoted to
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synchronization, so a transmission requires a total of 206 / 3
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+ 16 = 85 (rounded up) channel symbols. The sync symbols are those
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numbered 1, 2, 5, 10, 16, 23, 33, 35, 51, 52, 55, 60, 66, 73, 83, and
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85 in the transmitted sequence.
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Each symbol lasts for 6912 sample intervals at 12000 samples per
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second, or about 0.576 seconds. Tone spacing of the 9-FSK modulation is
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12000/6912 = 1.736 Hz, the inverse of the symbol duration. The total
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occupied bandwidth is 9 × 1.736 = 15.6 Hz.
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